The definition of context diagram is the highest level in a data flow diagram and contains only one process, representing the entire system. The process is given the number zero. All external are shown on the context diagram, as well as major data flow and from them.
The diagram does not contain any data stores and is fairly simple to create, once the external entities and the flow to and from them are known to analysts. The definition of data flow diagram level 0 is the explosion of the context diagram and may include up to nine process. Including more processes at this level will result in a cluttered diagram that is difficult to understand.
The reason why it difficult is because each of the process is numbered with an integer. Generally, the numbered starting from the upper left-hand corner of the diagram and working toward the lower right-hand corner. The context diagram also provided the abstract view of the information system. This is used for depicting the scope and boundary of the information system in context diagram external data source entities, processes are identified during system requirement. Aldo, for the data flow diagram level 0, there is providing deep insight view of a system and represents the major internal process, data flows and data stores. The relationship between both diagrams is the detailed description of the context diagram when the context diagram is expanded into data flow diagram level 0.
Then, all the data flow must be retain. It will implies there is a relationship between context diagram and data flow diagram level 0. Besides,